It can be desirable to sense the torque generated by an electric actuator. Some actuators use torque springs to achieve this objective. When torque springs are used, splined shafts are required to allow for sliding of the worm gear, which adds cost. That is, a sliding worm gear requires an expensive geared pinion to transfer rotary movement from the gearbox to the electrical enclosure, where a sensor can measure rotation of the torque pinion. This type of torque sensing system has many moving parts, and can be expensive and less accurate than direct force measurement systems.
Some actuator manufacturers use load cells to measure torque but the load cells are routinely placed in the gearbox or the motor cavity. This placement can be undesirable due to exposure to grease, oil, grime, high temperatures, etc. Placing a sensor directly on the motor shaft or worm shaft also exposes the sensor to harsh conditions, affecting the accuracy and driving up cost. Mounting a sensor on a rotating shaft also requires means to prevent rotation of the sensor, which additionally drives up cost. These locations also require wires to run from the gearbox or motor cavity to the electrical enclosure, making it difficult to maintain a seal between these spaces. This also increases the potential for exposure to electrical interferences to low level analog sensor signals.